The present invention relates to conduit systems for conveying hazardous waste material to incinerators, waste containers and the like and, more particularly, to gate valves integral with such conduit systems.
With availability of suitable sites for land fills near heavily populated areas diminishing, the use of incinerators as a means of safely disposing of waste becomes more desirable. In order to feed such incinerators efficiently and to comminute waste material to promote high-temperature combustion, auger shredders are used to feed such incinerators. For example, U.S. Pat. Nos. 4,253,615; 4,938,426 and 4,915,038 disclose auger shredders appropriate for use in feeding incinerators. Such auger shredders typically comminute or shred waste material into smaller particles, compress the material and force it into a feed conduit connected to the incinerator. The material forms a plug within the conduit which often acts as a barrier between the incinerator and the auger shredder to prevent burn back of the material through the conduit and the escape of hazardous gases through the conduit.
However, in may become necessary to effect a positive closure of the conduit connecting the auger shredder and incinerator such as, for example, when the auger shredder is not operating and the plug of material within the conduit is not moving toward the incinerator. Such closures typically take the form of a slide valve in which a flat plate slides into and out of alignment with the conduit to close and open, respectively, the passage between the auger shredder and the incinerator.
A disadvantage with such types of valves is that the material conveyed by the conduit quit often is hazardous, corrosive and includes abrasive particulates which can collect in the cavity occupied by the sliding member of such valves and corrode or otherwise jam the valve and valve plate.
Other types of valves are known, such as cut-off or gate valves. Such valves are disclosed in U.S. Pat. Nos. 1,099,200; 2,360,389; 3,047,006 and 3,237,916. Each of the valves disclosed in the aforementioned patents comprises a pair of housing members joined to each other at their peripheries to define a valve chamber which encloses a valve plate. The housing members are connected to a conduit so that material is directed through the conduit and a flow path in the valve body. The valve plate itself, or an orifice in the valve plate, is pivoted into and out of alignment with the flow path through the valve to open and close the valves.
However, a disadvantage with each of the aforementioned valves is that the action of opening and closing the valve by pivoting the valve plate acts to slice the plate through the plug of material in the flow path through the valve and displace a portion of that material into the valve chamber. Successive cycling of the valve plate causes the chamber to become full of such material, necessitating the manual removal of such material, which may be corrosive, toxic or otherwise hazardous.
Accordingly, there is a need for a valve which is suitable for use in an incinerator feed conduit, provides a positive closure and yet does not require frequent cleaning. Further, such a valve must be resistant to jamming and the accumulation of particulate material.